Grain growth inhibitor for superfine materials

ABSTRACT

A superfine material made by incorporation of an inorganic polymer precursor of a grain growth inhibitor into intermediates useful for the production of superfine materials. The precursor/nanostructured material composite is optionally heat treated at a temperature below the grain growth temperature of the superfine material in order to more effectively disperse the precursor. The composites are then heat treated at a temperature effective to decompose the precursor and to form superfine materials having grain growth inhibitors uniformly distributed at the grain boundaries. Synthesis of the inorganic polymer solution comprises forming an inorganic polymer from a solution of metal salts, filtering the polymer, and drying. Alloying additives as well as grain growth inhibitors may be incorporated into the superfine materials.

CROSS-REFERENCE TO RELATED APPLICATION

[0001] This application is a divisional application of U.S. Ser. No.09/138,137, filed Aug. 21, 1998, which claims priority to provisionalU.S. patent application Ser. No. 60/057,339, filed Aug. 22, 1997, whichis incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

[0002] 1. Field of the Invention

[0003] This invention generally relates to methods for the synthesis ofsuperfine materials having particle or gain dimensions larger than 100nm and less than or equal to about 10 microns. In particular, thisinvention relates to chemical methods for the introduction of a graingrowth inhibitor and/or alloy additions into superfine materials,resulting in materials having controlled microstructure and morphology.The obtained materials exhibit superior properties, including improvedfracture toughness, hardness, and wear-, corrosion-, anderosion-resistance.

[0004] 2. Brief Description of the Prior Art

[0005] For decades, materials with fine-scale microstructures have beenrecognized to exhibit unusual and technologically attractive properties.Currently, interest is growing in classes of materials composed of veryfine grains or particles having dimensions in the range of less than orequal to 100 nanometers (nm), known as “nanostructured” materials;materials composed of grains or particles having dimension in the rangeof greater than 100 nm and less than or equal to 1 micron, known as“ultrafine” materials; and a class of materials having dimensionsbetween about 1 micron and about 10 microns. As used hereinafter,“superfine” materials will refer collectively to materials havingdimensions of greater than 100 nm and less than or equal to about 10microns. A feature of superfine materials is the high fraction of atomsthat reside at grain or particle boundaries compared to largermaterials. Nanostructured and superfine materials may thus havesubstantially different, often superior chemical and physical propertiescompared to conventional, large-sized counterparts having the samecomposition. Thus considerable advantages accrue from the substitutionof nanostructured and superfine materials for conventionallarge-structured materials in a wide range of applications, for examplesuperior strength, improved fracture toughness and hardness inmartensitic steels, and reduced sintering temperature for consolidationand the onset of superplasticity in ceramics. Nanostructured andsuperfine metal alloys and metal carbides, in particular, are expectedto have superior properties, including improved fracture toughness,hardness, and wear-, corrosion-, and erosion-resistance. The ability tosynthesize and optimize the pore structure and packing density ofnanostructured and superfine materials at the atomic level is a powerfultool for obtaining new classes of these materials. These new classes,together with designed multifunctional coatings, present unprecedentedopportunities for advances in material properties and performance for abroad range of engineering applications.

[0006] Inframat Corp. has made significant progress in the field ofnanostructured and superfine materials, including in the synthesis ofnanostructured metal powders by the organic solution reaction (OSR)method, aqueous solution reaction (ASR) method, and in advanced chemicalprocessing of oxides and hydroxides materials for structural, batteryand fuel cell applications. Examples of materials produced from thesemethods include nanostructured alloys of Ni/Cr, nanostructuredNiCr/Cr₃C₂ composites, nanostructured yttria-stabilized ZrO₂,nanofibrous MnO₂, and Ni(OH)₂. Inframat has further developedtechnologies for manufacturing nanostructured and ultrafine materials inbulk quantities as disclosed in “Nanostructured Oxide and HydroxideMaterials and Methods of Synthesis Therefor,” which is the subject ofpending U.S. and foreign applications (including U.S. Ser. No. 08/971,filed Nov. 17, 1997), as well as technologies for the thermal spray ofnanostructured and ultrafine feeds including nanostructured WC—Cocomposites, as disclosed in “Nanostructured Feeds for Thermal SpraySystems, Method of Manufacture, and Coating Formed Therefrom” also thesubject of pending U.S. and foreign patent applications (including U.S.Ser. No. 09/019,061, filed Feb. 5, 1998), both U.S. patent applicationsbeing incorporated herein in their entirety. Chemical syntheses ofnanostructured metals, ceramics, and composites using OSR and ASRmethods have also been previously described by Xiao and Strutt in“Nanostructured Metals, Metal Alloys, Metal Carbides and Metal AlloyCarbides and Chemical Synthesis Thereof,” U.S. Ser. No. 08/989,000,filed Dec. 5, 1996, incorporated herein by reference, as well as in“Synthesis and Processing of Nanostructured Ni/Cr and Ni—Cr₃C₂ Via anOrganic Solution Method,” Nanostructured Mater. Vol. 7 (1996) pp.857-871 and in “Synthesis of Si(C,N) Nanostructured Powders From anOrganometallic Aerosol Using a Hot-Wax Reactor,” J. Mater. Sci. Vol. 28(1993), pp. 1334-1340.

[0007] The OSR and ASR methods employ a step-wise process generallycomprising (1) preparation of an organic (OSR) or aqueous (ASR) solutionof mixed metal halides; (2) reaction of the reactants via sprayatomization to produce a nanostructured precipitate; and (3) washing andfiltering of the precipitate. The precipitate is often then heattreated, and/or subjected to gas phase carburization under eithercontrolled carbon/oxygen activity conditions (to form the desireddispersion of carbide phases in a metallic matrix phase), or undercontrolled nitrogen/hydrogen activity conditions to form nanostructurednitrides. This procedure has been used to synthesize variousnanostructured compositions, including nanostructured NiCr/Cr₃C₂ powdersfor use in thermal spraying of corrosion resistant hard coatings. Anadvanced chemical processing method combines the ASR and OSR methodswith spray atomization and ultrasonic agitation.

[0008] Another approach to the synthesis of nanostructured materials isthe inert gas condensation (IGC) method. As described in “Materials withUltrafine Microstructures: Retrospective and Perspectives”,Nanostructured Materials Vol. 1, pp. 1-19, Gleiter originally used thismethod to produce nanostructured metal and ceramics clusters. The methodwas later extensively used by Siegel to produce nanostructured TiO₂ andother systems, as described in “Creating Nanophase Materials”,Scientific American Vol. 275 (1996), pp.74-79. This method is the mostversatile process in use today for synthesizing experimental quantitiesof nanostructured metals and ceramic powders. The IGC method uses anevaporative sources of metals, which are then convectively transportedand collected on a cold substrate. Ceramic particles must be obtained byinitially vaporizing the metal source, followed by a slow oxidationprocess. A feature of this method is the ability to generate looselyagglomerated nanostructured powders, which are sinterable at lowtemperatures.

[0009] One other method for the synthesis of nanostructured materials ischemical vapor condensation (CVC). CVC is described by Kear et al. in“Chemical Vapor Synthesis of Nanostructured Ceramics” in MolecularlyDesigned Ultra fine/Nanostructured Materials in MRS Symp. Proc. Vol. 351(1994), pp. 363-368. In CVC, the reaction vessel is similar to that usedthe IGC method, but instead of using an evaporative source, a hot-walltubular reactor is used to decompose a precursor/carrier gas to form acontinuous stream of clusters of nanoparticles exiting the reactor tube.These clusters are then rapidly expanded out to the main reactionchamber, and collected on a liquid nitrogen cooled substrate. The CVCmethod has been used primarily with chemical precursors or commerciallyavailable precursors. Kear describes the production of nanostructuredSiC_(x)N_(y) and oxides from hexamethyldisilazane.

[0010] Finally, a thermochemical conversion method for producingnanostructured WC—Co has been disclosed by Kear in “Synthesis andProcessing of Nanophase WC—Co Composite” Mater. Sci. Techn. Vol. 6(1990), p. 953. In this method, aqueous solutions containing tungstenand cobalt precursors are spray-dried to form an intermediate precursorat temperatures of about 150 to 300° C. This intermediate precursor is amixture of amorphous tungsten oxide and cobalt in the form of aspherical hollow shell having a diameter of about 50 microns and a wallthickness of about 10 microns. Nanostructured WC—Co is then obtained bythe carburization of this precursor powder at 800-900° C. in a carbonmonoxide/carbon dioxide mixture. The synthesis of nanostructured WC/Cousing this technique has described in several patents by McCandlish etal., including “Multiphase Composite Particle,” U.S. Pat. No. 4,851,041,and “Carbothermic Reaction Process for Making Nanophase WC—Co,” U.S.Pat. No. 5,230,729. Synthesis of nanostructured and superfine WC/Co isof particular interest to industry, as is it is presently the materialof choice for cutting tool, drill bit, and wear applications.

[0011] It is expected that a number of the techniques developedespecially for nanostructured materials are also applicable to synthesisof superfine materials, through controlled manipulation of grain sizeeither at the synthetic level or through the use of grain growthinhibitors. However, a major drawback of the above-described techniques,as well as for other techniques for the synthesis of superfine materialsknown in the art, is the tendency of the produced materials to undergouncontrolled grain growth during sintering or use of the nanostructuredcomponent, especially at high temperature. For example, the tungstencarbide grains of as-synthesized nanostructured WC—Co have diameters ofabout 30 nm. During liquid phase sintering, the tungsten carbide grainsgrow rapidly to diameters of several microns or larger in a relativelyshort time, e.g., a few minutes. After exhaustive research andengineering evaluations it has been concluded that VC and/or Cr₃C₂ arethe most effective carbide phases of the very large range of materialsevaluated over the years.

[0012] Vanadium carbide, for example, has been employed by Nanodyne,Inc. (Brunswick, N.J.) to prevent this disadvantageous grain growth, asdescribed in Nanodyne's product specification for the product sold underthe tradename Nanocarb®. In this process, micron-sized vanadium carbidepowders are blended into the WC/Co powder composite via mechanicalmixing, followed by shape-formation and sintering into bulk components.The use of vanadium carbide is effective to prevent some degree of graingrowth, as the final grain size of the consolidated bulk piece is in thesub-micron range, e.g., 0.2-0.8 microns. The major drawback of thisgrain growth technique is the non-homogeneous mixing of the VC withinthe WC/Co composite materials as well as the difficulty of sinteringkinetics, resulting in non-homogeneous bulk material properties, orincreased cost for sintering procedure.

[0013] In an attempt to solve the above problem, Nanodyne currentlyemploys a chemical precipitation technique in which a vanadium salt isintroduced chemically at the start of the materials synthesis. Althoughuse of this technique overcomes the problem of non-homogeneous mixing,it produces vanadium oxide instead of vanadium carbide. It is well knownthat any oxide material that presented in the WC/Co system isdetrimental to the material. The introduction of vanadium oxide into theWC/Co system not only creates sintering difficulties, but also requiresan extra carbon source in the WC/Co powder for the conversion ofvanadium oxide into vanadium carbide at extremely high temperatures,e.g., 1450° C. In many cases the extra carbon source embrittles theconsolidated materials.

[0014] Prior incorporation of boron compounds into fine-grainedmaterials has been described in “Synthesis of AlN/BN CompositeMaterials” by Xiao and Strutt, in J. Am. Ceram. Soc., Vol. 76, p. 987(1993), which discloses synthesis from a composite precursor comprisingaluminum, boron, and nitrogen. The boron nitride polymer is formed bybubbling ammonia into an aqueous solution of boric acid and urea.

[0015] Scoville et al., in “Molecularly DesignedUltrafine/Nanostructured Materials”, ed. by K. E. Gonsalves, D. M. Chow,T. D. Xiao, and R. Cammarato, MRS Symp. Vol. 351, p. 431 (1994) describea method for incorporation of BN nanostructured particles into agermanium crystal lattice to significantly reduce thermal conductivity.In this method, micron-sized BN and Si/Ge powders are blended togetherand evaporated using a plasma torch to form mixtures, which are thencondensed into a composite of BN/Si/Ge. Heat treatment results in largecrystals (>1 micron) of Si/Ge wherein discrete 2-10 nm BN grains aretrapped inside the large crystals.

[0016] Boron nitride has also been incorporated into a conventional(larger than 100 nm grain size) titanium diboride system with WC/Coadditives as disclosed in U.S. Pat. No. 5,632,941 to Mehrotra et al. BNis incorporated in the form of a powder. U.S. Pat. No. 4,713,123 furtherdisclose use of BN as a grain growth inhibitor in conventional (largerthan 100 nm grain size) silicon steel. However, when the quantity of BNis too large, it is becomes difficult to grow the secondaryrecrystallized grain with {110}<001>orientation, so that the amount islimited to a range of 0.0003-0.02%. Addition of boron to silicon steelin the form of ferroboron, followed by nitridation of the steel toprovide nitrogen results in the formation of slight amounts of boron orBN, which may inhibit grain boundary migration, as reported by Grenoblein IEEE Trans. Mag., May 13th, p. 1427 (1977), and Fiedler in IEEETrans. Mag. May 13th p. 1433 (1977). None of these references discloseuse of a BN polymer as a grain growth inhibitor precursor.

[0017] Accordingly, there remains a need in the art for methods ofinhibiting and/or controlling grain growth during the processing ofas-synthesized nanostructured and superfine materials and nanostructuredand superfine material intermediates, especially a method applicable toa wide range of compositions.

SUMMARY OF THE INVENTION

[0018] The above discussed and other drawbacks and deficiencies of theprior art are overcome or alleviated by the method of the presentinvention, comprising incorporation of a polymer precursor of a graingrowth inhibitor into superfine materials or intermediates useful forthe production of superfine materials. The precursor/nanostructured (orsuperfine) material composite is optionally heat treated at atemperature below the grain growth temperature of the material in orderto more effectively disperse the precursor. The composites are then heattreated at a temperature effective to decompose the precursor, therebyforming materials having grain growth inhibitors uniformly distributedtherein, preferably onto the grain boundaries. Synthesis of a preferredinorganic polymer solution comprises forming an inorganic polymer from asolution of metal salts, filtering the polymer, and drying.

[0019] In a first embodiment of the present invention, the inorganicpolymer precursor is introduced into the superfine material in thepowder production step, i.e., during the synthesis of the material or anintermediate leading to the product material, and then converted by heattreatment to the grain growth inhibition species, thus allowing thegrain growth species to be homogeneously mixed with the material at themolecular level. Such heat treatment may also be used to convert anintermediate superfine material into the product superfine material.

[0020] In a second embodiment, the polymeric precursor is incorporatedinto an already-synthesized superfine material or intermediate. In onemethod, the polymer precursor is dissolved into a solvent containing adispersion of already-synthesized particles and the resultant slurry isoven-dried or spray-dried to form a dried powder having the grain growthinhibitor uniformly distributed within the grain boundaries of thesuperfine particles. Alternatively, already-synthesized particles arecoated with the polymer precursor and optionally heat treated at atemperature lower than the grain growth temperature, thereby melting anddiffusing precursor through any matrix and to the grain boundaries. Theoven-dried, spray-dried or coated particles/precursor composites arethen heat treated if necessary to convert the polymer precursor to graingrowth inhibitor, and optionally further processed (e.g., by nitridationor carburization) to produce product materials having grain growthinhibitors uniformly distributed at the grain boundaries. Thismethodology is capable of substantially coating each particle with agrain growth inhibitor barrier, or of obtaining homogeneous mixing ofthe grain growth inhibitor with the nanoparticles at the nanometerlevel.

[0021] In still another embodiment of the invention, alloying additivesand/or grain growth inhibitors are incorporated into the materials. Thealloying additives and/or grain growth inhibitor precursor may beincorporated into the reaction mixture used to synthesize the materialas described in the above first embodiment, or the alloying additivesprecursor may be incorporated into the as-synthesized material asdescribed in the above second embodiment. The as-synthesized materialmay comprise grain growth inhibitor or precursor incorporated at thesynthesis stage. Alternatively, the alloying additive is combined withthe polymeric grain growth inhibitor precursor and then incorporatedinto the already-synthesized particles. Mixing, e.g., by ball-milling toform a homogeneous mixture of the particles with the alloying additivesand the grain growth inhibitor precursor is followed by spray drying oroven-drying and processing as described above for the second embodiment.

[0022] An especially advantageous feature of the present method is itsapplicability to a wide variety of materials systems, including metals,metal alloys, carbides, nitrides, intermetallics, ceramics, and theircombinations. Preferably, the grain growth inhibitor itself is a highperformance material, exhibiting excellent mechanical and other physicaland chemical properties. Addition of alloying additives further improvesthe properties of the product materials, including hardness, toughness,density, corrosion- and erosion-resistance. The present invention allowsthe economical, large-scale fabrication of high performance superfinematerials having a wide range of compositions for targeted applications.

BRIEF DESCRIPTION OF DRAWINGS

[0023]FIG. 1 is a graph illustrating the effect of increasing amounts(weight %) of BN on hardness of a WC—Co nanostructured compositematerial.

[0024]FIG. 2 shows the Vicker's hardness data of the samples from thethermal spray trials.

[0025]FIG. 3 is a graph illustrating the effect of the toughness asfunction of alloy addition with 1 wt. % BN grain growth inhibitor.

DETAILED DESCRIPTION OF THE INVENTION

[0026] The methods of the present invention are particularly useful forincorporation of grain growth inhibitors and/or alloying additives intosuperfine materials (materials having grain sizes greater than 100 nmand less than or equal to about 10 microns). Accordingly, the presentinvention is directed to a method for the inhibition of grain growthduring processing of powder materials, comprising incorporation of agrain growth inhibitor polymer precursor into superfine materials orintermediates useful for the production of superfine materials for bulkand coating applications. The polymer precursor and/or alloying additiveis incorporated into the superfine material or intermediate either asthe material is synthesized, or after synthesis (preferably at theas-synthesized intermediate stage). Incorporation of the polymerprecursor and optional alloying additive as the material is synthesizedis preferable, as the number of processing steps is reduced, the methodis more cost-effective, and it is more likely that the grain growthinhibitor is uniformly distributed. The present invention thereforeprovides a method for fabricating superfine materials with controlledmorphology, microstructure, and chemical composition. The materialobtained can be used as feed stocks for superfine coatings as well as inadvanced, high performance bulk applications.

[0027] Without being bound by theory, it is hypothesized that thesurprisingly good results obtained by the present invention arise fromeffective distribution of the grain growth inhibitor substantially ontothe grain boundaries, as such distribution minimizes grain growth due tothe difficult diffusion path for atoms across the grain boundaries. Withreference to the BN grain growth inhibitor in the WC/Co system inparticular, cluster stabilization in the cobalt-rich melt by thepresence of a high concentration of metal/non-metal binding pairs may bean important factor, since it inhibits liquid phase transport oftungsten and carbon from one WC grain to the next adjacent grain. Uponaddition of BN to the Co melt BN may pass into solution in the liquidCo; under these circumstances the melt, which is already rich intungsten and carbon in the case of nanophase material, would becomefurther enriched in boron and nitrogen, so that the potential forcluster stabilization is enhanced. Withe the addition of alloyingadditives such as Cr, Si, and the like, the complexity of the meltincreases, giving rise to the so-called “confusion” principle, whichdetermines the susceptibility of t a liquid melt to amorphization. Boronis a well-known melt depressant of transition elements, and AlliedSignal's METGLASS™ technology uses addition of boron to iron, nickel,and cobalt. In the present instance, boron may also be playing a role asa melt depressant, rendering the compacted material more susceptible todensification at low temperatures, as well as promoting amorphizationduring subsequent cooling. An alternative possibility is that nitrogenreacts with the WC interfaces to forma passivation film of W₂N or atungsten carbon nitride. In either case, the effect would be to inhibitcoarsening due to the presence of the passivation film.

[0028] Superfine materials suitable for use in the present inventioninclude metal, metal alloys, metal ceramics (especially metal carbidesand metal nitrides), intermetallics, ceramics, or ceramic-ceramiccomposites. More particularly, preferred superfine materials areselected from the group consisting of Cu, FeCu, FeCo, NiAl, MoC, MoSi,NiCr, TiC, Mo₂Si, NiCr/Cr₃C₂, Fe/TiC, Ni/TiC, Mo/TiC, and WC/Co, theforegoing alloyed with one or more of Ti, Cr, Mo, Ni, Zr, Ce, Fe, Al,Si, V, TiC, Mn, Y, W, and mixtures of the foregoing metals, metalalloys, intermetallics, and metal ceramics. Sulfide-metal systems areexcluded from the foregoing list.

[0029] Grain growth inhibitors suitable for use in the present inventionare preferably chemically inert, amenable to uniform distribution ontoor at the grain boundaries of the superfine material, and preferably addto, or at least do not detract substantially from, the chemical,physical, and mechanical properties desired in the superfine material.Importantly such inhibitors must also be available in a precursor formsuitable for incorporation into superfine materials. A particularlyimportant and advantageous feature of the present invention is that thegrain growth inhibitors are incorporated into the superfine material inthe form of a soluble, preferably water-soluble, polymeric precursor, orin the form of a low-melting polymer precursor. Use of a solubleprecursor allows more homogenous distribution of the precursor (and thusgrain growth inhibitor) throughout the superfine material. Use of alow-melting polymer precursor, i.,e., a precursor that melts atemperature below the grain growth temperature of the superfinematerial, also allows more homogenous distribution of the precursorthroughout the superfine material. Of course, the precursor must becapable of subsequent conversion to the grain growth inhibitor upontreatment, preferably upon heat treatment.

[0030] Suitable grain growth inhibitors having the above characteristicsmay include, but are not limited to those known in the art, includingmetals, metal alloys, carbides, nitrides, intermetallics, and ceramics.Particular grain growth inhibitors include metals such as B, Si, Al, Cr,Ni, Mo, Hf, Ta, Fe, W, Zr and rare earth metals such as Ce, La and Sm;metal alloys such as the foregoing alloyed with, for example, Cr, Ti,and Mo; carbides such as silicon-based carbides and titanium-basedcarbides; nitrides such as aluminum-based nitrides, titanium-basednitrides, and BN; intermetallics, including metal silicides such as AlSiand TiSi, and metal aluminides such as TiAl; and other boron compoundssuch as titanium diboride. Boron compounds, and particularly boronnitride is presently preferred, due to its ready synthetic availability,its favorable distribution characteristics, its chemical inertness, andits superior chemical, physical, and mechanical properties.

[0031] Synthesis of a polymer precursor which will yield a grain growthinhibitor generally comprises forming an inorganic polymer from asolution of metal salts, filtering the polymer, and drying the polymerto obtain a dried polymer precursor. In the case of boron nitride, theappropriate stoichiometric ratio of boric acid and urea is dissolved ina solvent, preferably in water. A nitriding gas such as ammonia is thenbubbled through the solution, making it strongly basic, until the metalprecursor salts have been converted into an inorganic polymer precursorwhich will yield boron nitride upon heat treatment. The product is driedto yield a precursor polymer gel, which can be stored in the dry form.

[0032] A first embodiment of the present invention comprises the in-situincorporation of the polymer precursor into the superfine products orsuperfine intermediates (usually a powder) as the superfine materials orintermediates are synthesized. Suitable synthesis techniques include butare not limited to those known in the art such as OSR, ASR, IGC, CVC,mechanical alloying, or other physical and chemical techniques. OSR andASR techniques are presently preferred. In this embodiment, the polymerprecursor is dissolved into a solvent, preferably water, containing thesuperfine material precursor(s) at controlled temperature in ratiosselected as appropriate for the desired product. While dissolving thesalts, the pH of the solution is controlled to prevent prematurereaction of the salts.

[0033] The resulting solution is then spray-dried or oven dried,depending on the material's application, to form a solid, driedsuperfine powder product or intermediate. The spray drying process isgenerally a preferred process. Control of the spray-drying parametersallows formation of different powder morphologies, including sphericalhollow shells and solid spheres of varying porosity and structure.During the drying process, the solution droplets reach elevatedtemperatures and become more concentrated as the solvent evaporates.Some or complete conversion of polymeric precursor to grain growthinhibitor may occur during spray-drying or oven-drying.

[0034] If required these dried powders are then treated, preferably heattreated, optionally under conditions of reduction and carburization ornitridation where required to produce the desired superfine product. Thegrain growth inhibitor precursor is partially or completely converted atthis step to the grain growth inhibitor. Selection of appropriatecarburization or nitridation conditions is well within the skill ofthose in the art, and requires the selection of an appropriatetemperature and gas ratio with controlled C, O, or N activity in orderto develop the desired particle size distribution, for example reductionof the oxide with amnmonia/hydrogen gas at elevated temperature (e.g.,600-800° C.).

[0035] In a second embodiment of the present invention, the polymerprecursor is incorporated into already-synthesized superfine materialsor superfine intermediate materials. This embodiment comprises coatingsuperfine particles (such as the subparticles of superfine WC/Co) withthe polymeric precursor and heat treating the coated materials ifnecessary at a temperature lower than the grain growth temperature ofthe material, thereby resulting in diffusion of the polymeric precursorthrough any matrix of the material and onto the grain boundaries. Thecombined polymer precursor-nanostructured material or intermediatecomposite is then treated, preferably heat treated, under controlled gasconditions at elevated temperature in order to decompose the polymerprecursor and to further diffuse the grain growth inhibitor to the grainboundaries.

[0036] In particular, the polymer precursor is either melted ordissolved directly onto the superfine material or intermediate, which ispreferably in powder form. The polymer precursor is preferably dissolvedin a solvent and added to either the superfine material or a slurry ofthe material. Where the particles are small enough or porous enough toallow sufficiently fine distribution of the polymer precursor throughoutthe material, a solution of appropriate concentration of precursor isused to wet the powder, and the resultant powder is simply air- oroven-dried onto the powder. Alteratively, the coated superfine particlesare heat-treated for a time effective to disperse the polymer precursorinto the superfine material or intermediate, at a temperature lower thanthe grain growth temperature of the superfine material.

[0037] Where the superfine particles are smaller than the desired finalpowder size, spray drying of a slurry of the polymer precursor andsuperfine material enhances diffusion and results hollow or solidspherical agglomerates having diameters in the range of 1-200 microns.Spray drying of the slurry results in the formation of a dried powderwherein the grain growth inhibitor is substantially uniformlydistributed onto the grain boundaries of the superfine particles. Thedried

[0038] powder is in the form of solid spheres having diameters in therange of about 1 to 200 microns, each sphere comprising an assemblage ofindividual superfine particles.

[0039] Where necessary the coated material, whether spray-dried,oven-dried, or air-dried, is then treated, preferably heat treated in acontrolled gas environment at elevated temperatures, to decompose theinhibitor precursor, and to further diffuse the inhibitor atoms throughany matrix material (if present) onto the grain boundaries of thesuperfine particles. Carburization or nitridation may also occur at thisstep. Subsequent processing of the composite superfine powders in acontrolled environment results in the formation of either bulk materialsor coatings with superior properties.

[0040] In another embodiment of the present invention, at least onealloying additive is incorporated into the superfine material with orwithout incorporation of a grain growth inhibitor. The alloying additivecan be any metallic or ceramic powder effective to alloy with thesuperfine material by the below-described or other process, and whichdoes not significantly adversely affect the action of the grain growthinhibitor if present. Suitable alloying additives include, but are notlimited to, Ti, Cr, Mo, Ni, Zr, Ce, Fe, Al, Si, V, TiC, Mn, Y, W, alloysof the foregoing, nitrides of the foregoing, and intermetallics of theforegoing.

[0041] The alloying additives may be introduced at virtually any pointin the method of the present invention. Thus, alloying additives may beintroduced into the reaction mixture used to synthesize the superfinematerial or superfine intermediate material, and if present, graingrowth inhibitor precursor then incorporated either before (firstembodiment above) or after (second embodiment above) synthesis of thesuperfine material or superfine intermediate material. The alloyingadditives may also be incorporated into the already-synthesizedsuperfine material or superfine intermediate material, which synthesisalso incorporates grain growth inhibitor precursor if present asdescribed in the first embodiment above. Preferably the alloyingadditive and grain growth inhibitor precursor is incorporated into anas-synthesized superfine material or superfine intermediate materialsimultaneously.

[0042] One suitable method for this preferred method of incorporation isby ball milling the at least one alloying additive to obtain a moreuniform powder mixture and then dispersing the alloying additive(s) intoa solution containing the inorganic polymeric grain growth inhibitor,thereby forming a colloidal solution. The superfine material orsuperfine intermediate material is then mixed with the colloidalsolution, and the resultant solution is spray-dried or oven-dried. Thealloying additive(s) can also be introduced into the already-synthesizedmaterial or intermediate material by ball milling the alloying additivetogether with the superfine materials, followed by incorporation of thepolymeric grain growth inhibitor as described above in connection withthe second embodiment.

[0043] An apparatus suitable for the synthesis and introduction of aprecursor into a superfine material includes a solution reaction vessel,ball milling apparatus or an ultrasonic processing system, a spraydryer, equipped with the usual and necessary accessories such as pHmeter, temperature and gas flow controls, vacuum systems, as well as ahigh temperature carburization unit (fixed bed, moving bed, or fluidizedbed reactor).

[0044] The carburization or nitridation equipment can be fixed bedreactors, fluidized bed reactors, and/or moving bed reactors. In thecarburization, reactive gas such as H₂, CO/CO₂, NH_(3,) acetylene, N₂,Ar can be used. In a fluidized bed reactor, the solid particles aresuspended by the fluidizing gas increasing the total volume and spacingthe particles so that they are in constant motion, and are notcontinuously contacting one another. The particles are thus constantlyexposed to the reactive gas, leading to much faster and efficientcarburization process, and reduced agglomeration of the spray driedparticles. An important advantage to using such a reactor is its abilityto manufacture large batch quantities of powder for commercial use. Froma production point of view, however, the moving bed reactor is thepreferred reactor, because the moving bed reactor is suitable for acontinuous production line, and may be more efficient in both energyconsumption and gas consumption.

[0045] The invention is further illustrated by the followingnon-limiting examples.

[0046] Example 1: Synthesis of a Grain Growth Inhibitor PolymerPrecursor.

[0047] Boric acid, H₃BO₃, and urea (NH₂)₂CO (Aldrich Chemical Company,Milwaukee, Wis.) were used as received. Initially, 61.831 g (1 mol) ofboric acid, and 63.784 g (1.062 mole) of urea were dissolved in 1 literof deoxygenated water. After thorough mixing, the aqueous solution wasslowly heated to 90° C. Ammonia was bubbled into the solution withvigorous stirring until the solution is strongly basic. After 4 hours ofreaction, the water was removed by distillation, leaving as a residuethe polymeric precursor in the form of an amorphous solid weighingapproximately 80 grams. It is hypothesized that in the presence ofammonia, boric acid reacts with urea to form a poly-urea-boron complex.This boron nitride precursor is a gel-like white resin that is highlysoluble in water, and which is readily ground into powder. Upon heatingto a higher temperature in the presence of ammonia, the gel willinitially melt at near 200° C., forming a foam-like glassy material, andupon continued heating at near 500-650 ° C. transform into BN in theform of a white powder.

[0048] Example 2: Incorporation of BN into Nanostructured Materials.

[0049] A known quantity of BN polymeric precursor synthesized asdescribed in Example 1 was first dissolved in distilled, deionized waterto make a nearly saturated solution. This solution was then combinedwith hollow shell nanostructured WC—Co (used as received from Nanodyne,Inc., New Brunswick, N.J.) and ball milled to produce a slurry. Themilled slurry was then dried in an oven at about 100° C. to removewater. A number of samples were prepared wherein the molar percent ofboron in the BN was 0.1%, 0.25%, 0.5%, 1%, 2%, 5%, and 10%. Converted toweight percent (wt. %), these values correspond to 0.006 wt. %, 0.015wt. %, 0.03 wt. %, 0.06 wt. %, 0.119 wt. %, 0.293 wt. %, and 0.569 wt. %of boron in BN, respectively.

[0050] Example 3: Sintering of Precursor/Nanostructured MaterialIntermediates

[0051] The milled samples of Example 2 (as well as a sample of WC—Copowder as received) were sintered by first pressing about 10 g of eachsample into 1.5 cm discs and then heat treating each sample at 1400° C.under flowing argon gas using a heating rate of 10° C./minute and adwell time of 0.5 hour. After heat treatment, the resultant pellets hadshrunk to approximately half of their original sizes, and had densifiedto varying degrees, up to about 99% density.

[0052] The Vicker's hardness values (VHN 300 g) of these samples areshown graphically in FIG. 1. The average hardness of the sample having0.0 wt. % of boron is about 2135, with the highest values up to 2228.All of these samples are reasonably tough. For example, when measuringconventional WC—Co (which has a VHN of 1200-1600), cracks at the comersof each diamond indentation always appear. No visible cracks at theindents in the nanostructured WC—Co materials appeared in any of thesamples examined.

[0053] Example 4: Solid Diffusion of Precursor into Grain Boundaries(Argon Treatment).

[0054] The milled samples of Example 2 having 1 molar % and 10 molar % Bin BN were heat treated under argon at 600° C. for 5 hours. The treatedpowders were then pressed into 1.5 cm pellets, and heat treated at 1400°C. under flowing argon gas using a heating rate of 10° C./minute and adwell time of 0.5 hour. After heat treatment, the resultant pellets hadshrunk to approximately half of their original sizes, and had densifiedto varying degrees up to about 99% density.

[0055] Example 5: Solid Diffusion of Precursor into Grain Boundaries(Hydrogen Treatment).

[0056] The milled samples of Example 2 having 1 molar % and 10 molar % Bin BN were heat treated under hydrogen at 600° C. for 5 hours. Thetreated powders were then pressed into 1.5 cm pellets, and heat treatedat 1400° C. under flowing argon gas using a heating rate of 10°C./minute and a dwell time of 0.5 hour. After heat treatment, theresultant pellets had shrunk to approximately half of their originalsizes, and had densified to varying degrees up to about 99% density.

[0057] Example 6: Solid Diffusion of Precursor into Grain Boundaries(Ammonia Treatment).

[0058] The milled samples of Example 2 having 1 molar % and 10 molar % Bin BN were heat treated under ammonia at 600° C. for 5 hours. Thetreated powders were then pressed into 1.5 cm pellets, and heat treatedat 1400° C. under flowing argon gas using a heating rate of 10°C./minute and a dwell time of 0.5 hour. After heat treatment, theresultant pellets had shrunk to approximately half of their originalsizes, and had densified to varying degrees up to about 99% density.

[0059] Example 7: Thermal Spray Trials.

[0060] The milled sample of Example 2 comprising 0.06 wt. % of boron wasprepared in large quantity (about 1 lb) for thermal spray trials. Thethermal spray trials were carried out with a Metro 9MB arc plasma spraygun. The spray conditions are summarized below. Stand off Primary GasRelative Relative Trial Distance Arc Current Flow Temp. Time No.(inches) Voltage (amps) (scfm) (A/scfm) (inch/scfm) 1 4 65 450 150 3.00.027 2 4 65 400 150 2.7 0.027 3 4 65 400 150 2.7 0.027 9 4 65 400 1502.7 0.027 10 4 65 450 200 2.3 0.020 11 2.5 65 450 200 2.3 0.013 12 4 65450 250 1.8 0.016 13 4 65 450 150 3.0 0.027 14 4 65 450 200 2.3 0.020 154 65 400 200 2.0 0.020 16 4 65 600 250 2.4 0.016

[0061] Physical properties of the thermally sprayed materials aresummarized below. Relative Wear HV300 Trial No. Resistance Desirability*HV300 HV300 HV300 HV300 (Average)  1 3 0.53 786 1051  855 898  2 2  3 91.00 1042  829 1377  1083   9 8 0.79 446 1215  622 761 10 1 0.24 618 836406 369 557 11 5 0.43 348 427 295 357 12 0.05 0.04 385 275 267 309 13 60.61 550 459 715 675 600 14 5 0.48 389 484 496 456 15 8 0.65 639 402 499513 16 1.5

[0062] SEM examination indicated that trial No. 3 yielded the materialwith the best bonding and microstructure. The Vicker's hardness valuesof these samples in cross-section and perpendicular to the coating weremeasured, and the results are summarized in FIG. 2. The data in FIG. 2shows the relationship of coating properties for different plasmaconditions in the thermal spray trials. The coating properties includerelative wear resistance, hardness and desirability.

[0063] Example 8: In-situ Synthesis of Nanostructured Powders with GrainGrowth Inhibitor

[0064] An aqueous solution was prepared by dissolving 22.64 g (7.70mmol) of (NH₄)₆W₃₉O₁₂.H₂O (ammonium metatungstenate), 9.88 g (34 m mol)of Co(NO2₃)₂.H₂O (cobalt nitrate) and 13.80 g (77 mol) of glucose in 20mL of water. A volume of aqueous solution comprising 12 mg (0.5 mmol) ofBN was added to the above aqueous solution. This reaction mixture wasthen spray dried to make a W—C—Co—BN pre-composite powder. Thisprecursor powder is then transferred into a high temperature furnace andcarburized under a mixture of H₂/CO gas using a heating rate of 10°C./min and reaction time of 30 minutes, thereby producing nanostructuredWC/Co comprising the BN grain growth inhibitor.

[0065] Example 9: In-situ Synthesis of Alloyed Nanostructured Powderswith Grain Growth Inhibitor

[0066] An aqueous solution was prepared by dissolving 22.64 g (7.7 mmol)of ammonium metatungstenate, 9.88 g (34 mmol) cobalt nitrite, and 13.80g ( 77 mol) glucose in 20 mL of water. A volume of aqueous solutioncomprising 12 mg (0.5 mmol) of BN polymeric precursor was added to theabove aqueous solution. A mixture comprising 0.2 g (3.3 mmol) of TiC,0.0002 g of Cr and 0.02 g (0.2 mmol) of Mo was then added to make areaction mixture comprising 0.06 wt % BN, 0.1 wt. % Mo, 0.01 wt. % Cr,and 1 wt. % TiC with respect to WC. This reaction mixture is then spraydried to make a W—C—Co—BN pre-composite powder containing the alloyingadditives. This precursor powder is then transferred into a hightemperature furnace and carburized under a mixture of H₂/CO gas using aheating rate of 10° C./min and reaction time of 30 minutes, therebyproducing nanostructured WC/Co alloyed with Ti, Cr, and Mo andcomprising the BN grain growth inhibitor.

[0067] Example 10: Alloy additives and BN Grain Growth Inhibitor intoNanostructured WC/Co

[0068] A series of compositions were prepared using 6 g (0.1 mol) TiC,0.06 g (1.2 mmol) Cr, 0.6 g (6.3 mmol) Mo, and 29 mL of a 1 molarsolution of the BN precursor added to 600 g of nanostructured WC/Cohaving varying amounts of Co (used as received from Nanodyne) to formcompositions having 1 wt. % TiC, 0.01 wt. % Cr, 0.1% Mo, and 0.06 wt. %BN with respect to WC/Co, where the Co varied from 6 to 15 wt. %. Thepowders were then thoroughly mixed via ball milling to form anintermediate powder composition, followed by either spray drying or ovendrying.

[0069] One part of the intermediate powder composition was spray driedto form spherical WC/Co composites containing BN grain growth inhibitorand the alloying additives. Such composites are useful either as thermalspray feedstock materials or for bulk consolidation.

[0070] Another part of the intermediate powder composition wasconsolidated into 1 cm discs via a hydraulic press, and heat treated at1400° C. under flowing H₂ gas using a heating rate of 10° C./minute anda dwell time of 0.5 hour. After heat treatment, the resultant pelletshad shrunk to approximately half of their original sizes, and haddensified to varying degrees up to near theoretical or 100% density. Thehardness of these WC/Co consolidated pellets comprising BN and Cr and Tialloying agents varies from 1900 up to 2400 VHN as the wt. % of Covaries from 15 wt. % to 6 wt. %. A comparison of the results of plottinghardness vs. Co content for nanostructured WC/Co containing the graingrowth inhibitor and alloy additives, and for nanostructured WC/Cowithout any alloy additives and/or grain growth inhibitor is shown inFIG. 3.

[0071] The toughness of the nanostructured WC/Co containing grain growthinhibitor and alloy additives is also increased relative to WC/Co withno grain growth inhibitor or alloying additives. For example, with nograin growth inhibitor or allying additives, typical WC-10Co has atoughness of 10-12 (MPa)·(meter^(1/2)), whereas the toughness of thenanostructured WC/Co containing alloy additives and the polymeric graingrowth inhibitor is from 15 to 30 (MPa)·(meter^(1/2)).

[0072] Example 11: Alloy Additives and BN Grain Growth Inhibitor intoSubmicron Sized WC/Co

[0073] Submicron-sized (0.2 micron) WC and micron-sized (1-5 micron) Cowere purchased from Dow Chemical. 6 g (0.1 mol)TiC, 0.06 g (1.2 mmol)Cr, 0.6 g (6.3 mmol) Mo, and 29 mL of an aqueous 1 molar solution of BNprecursor was added to 600 g submicron WC/Co, to make compositionshaving 1 wt. % TiC, 0.01 wt. % Cr, 0.1% Mo, 0.06 wt. % BN with respectto WC/Co, where the Co varies from 6 to 15 wt. %. The powders were thenthoroughly mixed via ball milling to produce intermediate powdercompositions which were either spray dried or oven dried.

[0074] Part of the intermediate powder composition was spray dried toform spherical WC/Co composite containing BN grain growth inhibitor andthe alloying additives. Such compositions are useful either as thermalspray feedstock materials or for bulk consolidation.

[0075] Part of the intermediate powder was also consolidated into 1 cmdiscs via a hydraulic press, and heat treated at 1400° C. under flowingH₂ gas using a heating rate of 10° C./minute and a dwell time of 0.5hour. After heat treatment, the resultant pellets had shrunk and haddensified to varying degrees up to near theoretical or 100% density. Thehardness of the produced pellet comprising WC/Co with alloy and graingrowth inhibitor varies from 1600 up to 1900 VHN, as the wt. % of Covaries from 15 wt. % to 6 wt. %.

[0076] Conventional alloying techniques have generally comprisedblending of micron-sized powders to form a mixture, followed by meltingat high temperature to obtain the alloyed material. In contrast, aparticularly favorable feature of the present invention is the use ofsoluble or low-melting grain growth inhibitor precursors and/or alloyingadditives to obtain uniform mixing with the superfine materials. It isalso possible to use these techniques to incorporate controlledquantities of grain growth inhibitors into nanostructured materials,thereby allowing the controlled growth of nanostructured particles tosuperfine particles.

[0077] While preferred embodiments have been shown and described,various modifications and substitutions may be made thereto withoutdeparting from the spirit and scope of the invention. Accordingly, it isto be understood that the present invention has been described by way ofillustration and not limitation.

What is claimed is:
 1. A superfine material, made by a method comprisingincorporating a grain growth inhibitor polymeric precursor into acomposition for the synthesis of a superfine material or superfineintermediate material; synthesizing the superfine material from thecomposition having the incorporated precursor to produce a superfinematerial/precursor composite or a superfine intermediatematerial/precursor composite; and treating the composite to convert theprecursor to a grain growth inhibitor.
 2. The superfine material ofclaim 1 , wherein the grain growth inhibitor is boron nitride and thesuperfine material is WC/Co.
 3. The superfine material of claim 2 ,wherein the grain growth inhibitor polymer precursor is synthesized bytreating a mixture of boric acid and urea in water with ammonia.
 4. Thesuperfine material of claim 1 , wherein synthesizing the superfinematerial/precursor composite or superfine intermediatematerial/composite is by aqueous solution reaction, inorganic solutionreaction, inert gas condensation, chemical vapor deposition, mechanicalalloying, or thermochemical conversion.
 5. The superfine material ofclaim 4 , wherein synthesizing is by aqueous solution reactioncomprising spray-drying or organic solution reaction comprisingspray-drying to form a superfine material intermediate/precursorcomposite in the form of a powder.
 6. The superfine material of claim 5, wherein treating is by heat-treating the powder at a temperature lessthan the grain growth temperature of the superfine material, therebypartially or fully converting the grain growth inhibitor precursor tothe grain growth inhibitor.
 7. The superfine material of claim 7 ,further comprising reducing, carburizing, or nitriding the superfinematerial intermediate/precursor composite to form the product superfinematerials or to convert the grain growth inhibitor precursor to thegrain growth inhibitor or a combination thereof.
 8. The superfinematerial of claim 1 , wherein treating is by heat-treating the superfinematerial/precursor composite or the superfine intermediatematerial/precursor composite at a temperature less than the grain growthtemperature of the superfine material or superfine intermediatematerial, thereby partially or fully converting the grain growthinhibitor precursor to the grain growth inhibitor.
 9. The superfinematerial of claim 1 , wherein the superfine material is selected fromthe group consisting of a metals, metal alloys, metal carbides, metalnitrides, metal ceramics, ceramics, ceramic-ceramic composites, orintermetallics.
 10. The superfine material of claim 1 , wherein thesuperfine material is selected from the group consisting of Cu, FeCu,FeCo, NiAl, MoC, MoSi, NiCr, TiC, Mo₂Si, NiCr/Cr₃C₂, Fe/TiC, Ni/TiC,Mo/TiC, WC/Co, the forgoing alloyed with one or more of Ti, Cr, Mo, Ni,Zr, Ce, Fe, Al, Si, V, TiC, Mn, Y, W, and mixtures thereof.
 11. Thesuperfine material of claim 1 , wherein the superfine material is WC/Co,WC/Co alloyed with at least one of TiC, Mo, Cr, or a combination thereof12. The superfine material of claim 1 , wherein the grain growthinhibitor is a metal, metal alloy, metal carbide, metal nitride,intermetallics, or ceramic.
 13. The superfine material of claim 1 ,wherein the grain growth inhibitor is selected from the group consistingof B, Si, Al, Cr, Ni, Mo, Hf, Ta, Fe, W, Zr, rare earth metals, Ce, La,Sm, the foregoing alloyed with Cr, TiC, Ti, and Mo or a combinationthereof, silicon-based carbides, titanium-based carbides, aluminum-basednitrides, titanium-based nitrides, BN; metal silicides, AlSi, TiSi,metal aluminides, TiAl and titanium diboride.
 14. The superfine materialof claim 1 , wherein the grain growth inhibitor is an inorganic boroncompound.
 15. The superfine material of claim 1 , wherein the graingrowth inhibitor is boron nitride.
 16. A superfine material, made by amethod comprising incorporating a grain growth inhibitor polymericprecursor into an already-synthesized superfine intermediate material;and treating the intermediate material to convert the precursor to agrain growth inhibitor.
 17. The superfine material of claim 16 , whereinthe grain growth inhibitor is boron nitride and the obtained superfinematerial is WC/Co.
 18. The superfine material of claim 17 , wherein thegrain growth inhibitor precursor is synthesized by treating a mixture ofboric acid and urea in water with ammonia.
 19. The superfine material ofclaim 16 , wherein the superfine material is selected from the groupconsisting of a metal, metal alloy, metal carbide, metal nitride, metalceramic, ceramic, ceramic-ceramic composite, or intermetallics.
 20. Thesuperfine material of claim 16 , wherein the superfine material isselected from the group consisting of Cu, FeCu, FeCo, NiAl, MoC, MoSi,NiCr, TiC, Mo₂Si, NiCr/Cr₃C₂, Fe/TiC, Ni/TiC, Mo/TiC, WC/Co, theforgoing alloyed with one or more of Ti, Cr, Mo, Ni, Zr, Ce, Fe, Al, Si,V, TiC, Mn, Y, W, and mixtures thereof.
 21. The superfine material ofclaim 16 , wherein the superfine material is WC/Co, WC/Co alloyed withat least one of TiC, Mo, Cr, or a combination thereof.
 22. The superfinematerial of claim 16 , wherein the grain growth inhibitor is a metal,metal alloy, metal carbide, metal nitride, intermetallics, or ceramic.23. The superfine material of claim 22 , wherein the grain growthinhibitor is selected from the group consisting of B, Si, Al, Cr, Ni,Mo, Hf, Ta, Fe, W, Zr, rare earth metals, Ce, La, Sm, the foregoingalloyed with Cr, Ti, TiC, and Mo or a combination thereof, silicon-basedcarbides, titanium-based carbides, aluminum-based nitrides,titanium-based nitrides, BN; metal silicides, AlSi, TiSi, metalaluminides, TiAl and titanium diboride.
 24. The superfine material ofclaim 23 , wherein the grain growth inhibitor is an inorganic boroncompound.
 25. The superfine material of claim 24 , wherein the graingrowth inhibitor is boron nitride.
 26. The superfine material of claim16 , wherein incorporating is by physical mixing of a solution of thegrain growth inhibitor precursor and the already-synthesized superfineintermediate material for a length of time effective for the graingrowth inhibitor precursor to diffuse into the material.
 27. Thesuperfine material of claim 16 , wherein incorporating is by heating ormelting the grain growth inhibitor precursor onto thealready-synthesized superfine intermediate material for a length of timeand at a temperature less than the grain growth temperature of thesuperfine material temperature but effective to promote diffusion of thegrain growth inhibitor precursor into the already-synthesized superfinematerial.
 28. The superfine material of claim 27 , wherein heating is ata temperature and for a length of time effective to convert the graingrowth inhibitor precursor to the grain growth inhibitor simultaneouswith diffusion, after diffusion, or a combination thereof.
 29. Thesuperfine material of claim 16 , wherein incorporating is by milling asolution of grain growth inhibitor precursor with thealready-synthesized superfine intermediate material.
 30. The superfinematerial of claim 16 , further comprising spray-drying a slurry of theincorporated grain growth inhibitor precursor and thealready-synthesized superfine intermediate material prior to heattreating.
 31. The superfine material of claim 16 , wherein heat treatingis in a controlled gas environment at a temperature effective todecompose the grain growth inhibitor precursor to the grain growthinhibitor.
 32. The superfine material of claim 16 , wherein theincorporating and the treating are performed at the same time by heattreatment for a length of time and a temperature effective to convertthe grain growth inhibitor precursor into the grain growth inhibitor,and to result in the grain growth inhibitor being diffused substantiallyonto the grain boundaries of the as-synthesized superfine intermediatematerial precursor.
 33. The superfine material of claim 32 , wherein thethe grain growth inhibitor is boron nitride.
 34. The superfine materialof claim 32 , wherein the already-synthesized superfine material isWC/Co, and the grain growth inhibitor is boron nitride.
 35. Thesuperfine material of claim 1 , further comprising incorporating atleast one alloying material into the composition for the synthesis of asuperfine material.
 36. The superfine material of claim 35 , wherein thesuperfine material is selected from the group consisting of metals,metal alloys, metal carbides, metal nitrides, metal ceramics, ceramics,ceramic-ceramic composites, or intermetallics; the grain growthinhibitor is selected from the group consisting of metal, metal alloys,metal carbides, metal nitrides, intermetallics, and ceramics.
 37. Thesuperfine material of claim 35 , wherein the superfine material isselected from the group consisting of Cu, FeCu, FeCo, NiAl, MoC, MoSi,NiCr, TiC, Mo₂Si, NiCr/Cr₃C₂, Fe/TiC, Ni/TiC, Mo/TiC, WC/Co, theforgoing alloyed with one or more of Ti, Cr, Mo, Ni, Zr, Ce, Fe, Al, Si,V, TiC, Mn, Y, W, and mixtures thereof; the grain growth inhibitor isselected from the group consisting of B, Si, Al, Cr, Ni, Mo, Hf, Ta, Fe,W, Zr, rare earth metals, Ce, La, Sm, the foregoing alloyed with Cr, Ti,TiC, and Mo or a combination thereof, silicon-based carbides,titanium-based carbides, aluminum-based nitrides, titanium-basednitrides, BN; metal silicides, AlSi, TiSi, metal aluminides, TiAl andtitanium diboride; and the at least one alloying additive is selectedfrom the group consisting of Ti, Cr, Mo, N, Zr, Ce, Fe, Al, Si, V, TiC,Mn, Y, W, alloys of the foregoing, nitrides of the foregoing, andintermetallics of the foregoing.
 38. The superfine material of claim 35, wherein the superfine material is WC/Co, the grain growth inhibitor isBN, and the alloying additive is Cr, TiC, and Mo.
 39. The superfinematerial of claim 16 , further comprising incorporating an alloyingmaterial into the already-synthesized superfine intermediate material.40. A superfine material, made by a method comprising incorporating agrain growth inhibitor polymeric precursor into a composition for thesynthesis of a nanostructured material or nanostructured intermediatematerial; synthesizing the superfine material from the compositionhaving the incorporated precursor to produce a nanostructuredmaterial/precursor composite or a nanostructured intermediatematerial/precursor composite; treating the composite to convert theprecursor to a grain growth inhibitor; and treating the nanostructuredmaterial or intermediate material to produce a superfine material orintermediate material.
 41. A superfine material, made by a methodcomprising incorporating a grain growth inhibitor polymeric precursorinto an already-synthesized nanostructured material or nanostructuredintermediate material; treating the nanostructured material orintermediate material to convert the precursor to a grain growthinhibitor; and treating the nanostructured material or intermediatematerial to produce a superfine material or intermediate material.
 42. Amethod of incorporating a grain growth inhibitor into a superfinematerial, comprising incorporating a grain growth inhibitor polymericprecursor, synthesized by treating a mixture of boric acid and urea inwater with ammonia, into an already-synthesized superfine material; andtreating the superfine material or intermediate material to convert theprecursor to a grain growth inhibitor.
 43. The superfine material ofclaim 42 , wherein the superfine material is selected from the groupconsisting of a metal, metal alloy, metal carbide, metal nitride, metalceramic, ceramic, ceramic-ceramic composite, or intermetallics.
 44. Thesuperfine material of claim 42 , wherein the superfine material isselected from the group consisting of Cu, FeCu, FeCo, NiAl, MoC, MoSi,NiCr, TiC, Mo₂Si, NiCr/Cr₃C₂, Fe/TiC, Ni/TiC, Mo/TiC, WC/Co, theforgoing alloyed with one or more of Ti, Cr, Mo, Ni, Zr, Ce, Fe, Al, Si,V, TiC, Mn, Y, W, and mixtures thereof.
 45. The superfine material ofclaim 42 , wherein the superfine material is WC/Co, WC/Co alloyed withat least one of TiC, Mo, Cr, or a combination thereof.
 46. The superfinematerial of claim 42 , wherein incorporating is by physical mixing of asolution of the grain growth inhibitor precursor and thealready-synthesized superfine material for a length of time effectivefor the grain growth inhibitor precursor to diffuse into the material.47. The superfine material of claim 42 , wherein incorporating is byheating or melting the grain growth inhibitor precursor onto thealready-synthesized superfine material for a length of time and at atemperature less than the grain growth temperature of the superfinematerial temperature but effective to promote diffusion of the graingrowth inhibitor precursor into the already-synthesized superfinematerial.
 48. The superfine material of claim 47 , wherein heating is ata temperature and for a length of time effective to convert the graingrowth inhibitor precursor to the grain growth inhibitor simultaneouswith diffusion, after diffusion, or a combination thereof.
 49. Thesuperfine material of claim 42 , wherein incorporating is by milling asolution of grain growth inhibitor precursor with thealready-synthesized superfine material.
 50. The superfine material ofclaim 42 , further comprising spray-drying a slurry of the incorporatedgrain growth inhibitor precursor and the already-synthesized superfinematerial prior to treating.
 51. The superfine material of claim 42 ,wherein treating is heat treating is in a controlled gas environment ata temperature effective to decompose the grain growth inhibitorprecursor to the grain growth inhibitor.
 52. The superfine material ofclaim 42 , wherein the incorporating and the treating are performed atthe same time by heat treatment for a length of time and a temperatureeffective to convert the grain growth inhibitor precursor into the graingrowth inhibitor, and to result in the grain growth inhibitor beingdiffused substantially onto the grain boundaries of the as-synthesizedsuperfine material.
 53. The superfine material of claim 42 , furthercomprising incorporating an alloying material into thealready-synthesized superfine material or superfine intermediatematerial.
 54. The superfine material of claim 53 , wherein the superfinematerial is selected from the group consisting of metals, metal alloys,metal carbides, metal nitrides, metal ceramics, ceramics,ceramic-ceramic composites, or intermetallics.
 55. The superfinematerial of claim 53 , wherein the superfine material is selected fromthe group consisting of Cu, FeCu, FeCo, NiAl, MoC, MoSi, NiCr, TiC,Mo₂Si, NiCr/Cr₃C₂, Fe/TiC, Ni/TiC, Mo/TiC, WC/Co, the forgoing alloyedwith one or more of Ti, Cr, Mo, Ni, Zr, Ce, Fe, Al, Si, V, TiC, Mn, Y,W, and mixtures thereof; and the at least one alloying additive isselected from the group consisting of Ti, Cr, Mo, N, Zr, Ce, Fe, Al, Si,V, TiC, Mn, Y, W, alloys of the foregoing, nitrides of the foregoing,and intermetallics of the foregoing.
 56. The superfine material of claim53 , wherein the superfine material is WC/Co, and the alloying additiveis at least one of Cr, TiC, and Mo.
 57. A superfine material comprisingan inorganic boron compound as a grain growth inhibitor, wherein thesuperfine material is selected from the group consisting of metalnitrides, metal ceramics, ceramics, ceramic-ceramic composites,intermetallics, Cu, FeCu, FeCo, NiAl, MoC, MoSi, NiCr, TiC, Mo₂Si,NiCr/Cr₃C₂, Fe/TiC, Ni/TiC, Mo/TiC, WC/Co, the forgoing alloyed with oneor more of Ti, Cr, Mo, Ni, Zr, Ce, Fe, Al, Si, V, TiC, Mn, Y, W, andmixtures thereof.
 58. The material of claim 57 , wherein the superfinematerial is WC/Co, the grain growth inhibitor is BN, and the alloyingadditive is at least one of Cr, TiC, and Mo.
 59. A superfine materialcomprising boron nitride as a grain growth inhibitor, wherein thesuperfine material is selected from the group consisting of metalnitrides, metal ceramics, ceramics, ceramic-ceramic composites,intermetallics, Cu, FeCu, FeCo, NiAl, MoC, MoSi, NiCr, TiC, Mo₂Si,NiCr/Cr₃C₂, Fe/TiC, Ni/TiC, Mo/TiC, WC/Co, the forgoing alloyed with oneor more of Ti, Cr, Mo, Ni, Zr, Ce, Fe, Al, Si, V, TiC, Mn, Y, W, andmixtures thereof.
 60. The material of claim 59 , wherein the superfinematerial is WC/Co, the grain growth inhibitor is BN, and the alloyingadditive is at least one of Cr, TiC, and Mo.
 61. A superfine alloycomprising one of Cu, FeCu, FeCo, NiAl, MoC, MoSi, NiCr, TiC, Mo₂Si,NiCr/Cr₃C₂, Fe/TiC, Ni/TiC, Mo/TiC, WC/Co alloyed with one or more ofTi, Cr, Mo, Ni, Zr, Ce, Fe, Al, Si, V, TiC, Mn, Y, and W.
 62. Asuperfine alloy comprising WC/Co alloyed with at least one of Cr, TiC,and Mo.